HP MLIB User's Guide Vol. 2 7th Ed.

Chapter 5 Fast Fourier Transforms 561
Simultaneous one-dimensional FFT SFFTS/DFFTS
VECLIB8:
INTEGER*8 l, incl, n, incn, iopt, ier
REAL*4 x(lenxy), y(lenxy)
CALL SFFTS(x, y, l, incl, n, incn, iopt, ier)
INTEGER*8 l, incl, n, incn, iopt, ier
REAL*8 x(lenxy), y(lenxy)
CALL DFFTS(x, y, l, incl, n, incn, iopt, ier)
Input x and y Arrays containing n data sets, each consisting of l data
points, to be transformed. Typically, x and y will be
two- or three-dimensional arrays with each data set
being a one-dimensional array section. Refer to “Notes”
for suggested usages.
Treating x and y as one-dimensional arrays results in
The real and imaginary parts of the i-th data point of
the j-th data set, 1 ≤ i ≤ l, 1 ≤ j ≤ n, are stored in
and
respectively.
l Number of data points in each data set, l > 0.
incl Storage increment between successive elements of the
same data set, incl > 0. Use incl = 1 if each data set is
stored contiguously in arrays x and y.
n The number of data sets, n > 0.
incn Storage increment between corresponding data points
of successive data sets, incn > 0.
iopt Option flag:
iopt ≥ 0 Compute forward transform.
iopt < 0 Compute inverse transform.
lenxy l 1–()incl× n 1–()incn× 1.++=
x i 1–()incl× j 1–()+ incn× 1+()
y i 1–()incl× j 1–()+ incn× 1+(),